Booting a computer refers to a process of loading an initial piece of software that starts the computer. Because the computer operating system (OS) is essential for running all other programs, the OS is usually the first piece of software that is loaded. During the boot process, the OS is typically copied from a permanent memory location (e.g., a hard disk) to an impermanent memory location (e.g., random access memory (RAM)). In some specialized computers, such as embedded systems, the OS is copied into a RAM disk.
A RAM disk is a memory-resident program which mimics a hard disk drive using part of the computer's RAM to store data which can be accessed as files. Unfortunately, RAM disks are not typically available in general purpose computers. Implementing a RAM disk has typically required significant effort by the computer user to retrofit the OS. As a result, traditional RAM disks are not readily realized or sufficiently robust to handle optical media formats.
A RAM disk acts as a virtual drive on the computer. A RAM disk allows one to create directories, copy files to and from memory, and so on. The data however is not written onto a hard disk, but remains purely stored into a particular part of RAM. Because physical disks have mechanical parts that allow for seeking to a particular position on the magnetic storage media and to read and write data, physical disks are relatively slow. In some cases, a RAM disk can read and write the same data thirty to sixty times faster than a hard disk. However, the data stored in RAM is “volatile”, meaning that the data disappears when power is removed from the RAM.
Unfortunately, traditional RAM disks do not easily allow for representations of software programs embodied on optical media. A primary reason for this is that traditional RAM disks use a cylinder/head/sector format, which is the format traditionally used by disk drives. Thus, for example, a volume accessed by a traditional RAM disk may be a snapshot of an actual system volume on a physical disk and partition in a hard disk drive. Because traditional RAM disks employ a cylinder/head/sector format, and optical media employ a different format (e.g., universal disk format (UDF) or ISO-9660 format), an optical media disk cannot be exactly represented by a traditional RAM disk.
The inability to exactly represent optical media using a traditional RAM disk is a substantial drawback, particularly when considering that the most commonly used form factor for booting the OS outside of the hard disk itself is the compact disc (CD), and may soon be the digital video disk (DVD), both of which are optical media. Transferring an operating system image from optical media to a traditional RAM disk format and accessing the media from the traditional RAM disk may not be simple and may incur unnecessary costs.
In addition, some computers may not have an optical media drive, or the optical media drive may be unavailable for booting the OS. In such circumstances, a program may not be exactly represented in a RAM disk if the program is provided on optical media (e.g., CD or DVD). The requirement for a physical CD in such situations can be a burden. As such, traditional RAM disk approaches do not provide the flexibility and robustness often desired by computer users.